Population Growth & Decline

Why we love it

Population is so much more than numbers. Its growth drives demand for housing, jobs, food, education, transportation and services. Its decline puts pressure on local business, government, housing and people. We love how this map shows the growth/decline pattern and gives a sense of urban, suburban and rural population density. It illustrates the story that most US cities are emptying out in an ever-expanding bubble called the suburbs.

Why it works

This map could be used as a backdrop for any organisation showing locations, services areas or other subjects. It shows you population growth and decline in a clear light. Red areas will lose population by 2015, while green areas will grow. Darker green areas will grow more than 1.25 percent per year. You can click on the map for details about an area. There is also a simple app showing this web map. You can download the data from the map package.

Important steps

Combine data

Working within ArcMap, take any dataset containing a population count for two different years.

Create fields

Add three new fields: Decline, Normal Growth (<1.25%), and High Growth (>1.25%).

Select population changes

Select all records where population change is > 1.25%.

Do the math

For each field, calculate the number of people predicted to increase or decrease. Use this value to set the dot density renderer in ArcMap using each of the three columns. The map package MXD file uses a set of scale-dependent renderers to pattern from.

Requirements

Data & Software

You will need numerical data to make a map that depicts change: The numeric difference between two time periods shows whether something is increasing or decreasing. You can use stronger colours to denote larger amounts of change. Software used: ArcGIS Desktop, ArcGIS Online.

Analysis

In each area, calculate the predicted increase or decrease in the number of people. Use this value to set the dot density renderer in ArcMap for each column (decrease, increase up to 1.25%, large increase > 1.25%).

Time

In ArcMap, it takes one hour to author the map, plus time to cache the results to a server or organisation account.

Tips and tricks

Make the map light or dark

Use a very light or very dark basemap when making dot density maps to help draw out the subtle patterns.